The present invention relates to a method for making silicone-poly(arylcarbonate) block copolymers by effecting reaction between a polyarylcarbonate oligomer having terminal hydroxylaryl groups and a polydiorganosiloxane having terminal chlorodiorganosiloxy groups in the presence of an organic solvent and an acid acceptor.
Prior to the present invention, as shown by Vaughn, U.S. Pat. No. 3,189,662, assigned to the same assignee as the present invention and incorporated herein by reference, silicone-polycarbonate block copolymers were made by phosgenating a mixture of dihydric phenol terminated polydiorganosiloxane, and dihydric phenol in the presence of an organic solvent and an acid acceptor. Although Vaughn's method results in the production of silicone-polycarbonate block copolymers useful in a variety of applications, such as injection moldable thermoplastics and elastomers having improved tensile properties, the method requires the use of phosgene gas. As a result, industry is constantly seeking new procedures for producing silicone-poly(arylcarbonate) block copolymers.
The present invention is based on the discovery that silicone-poly(arylcarbonate) block copolymers can be made without directly using phosgene gas in the final synthesis of the block copolymer by using a hydroxyl-terminated polyarylcarbonate oligomer having an average of about 2 to 1000 chemically combined arylcarbonate units. The hydroxylaryl terminated polyarylcarbonate oligomer, or "hydroxyaryl oligomer" is, thereafter, intercondensed with a chlorine terminated polydiorganosiloxane using an acid acceptor and an organic solvent.